Intradomain Gateway to Gatekeeper Security -This security is based on H.235, in which H.323 calls are authenticated, authorized, and routed by a gatekeeper. The gatekeeper is considered a known and trusted entity. The gateway does not authenticate it when the gateway tries to register with it.

Interdomain Gatekeeper to Gatekeeper Security -This security covers authenticating and authorizing of H.323 calls between the administrative domains of Internet Telephone Service Providers (ITSPs) using InterZone Clear Token (IZCT). This document covers only the portion of a call where the terminating gatekeeper sends a token in its location confirmation (LCF) message so that it authenticates the answerCall Admission Request (ARQ). Location request (LRQ) validation is not included in this feature. LRQ validation is a feature scheduled for a future Cisco IOS release.